The present invention relates to a method for regenerating a soot filter of a Diesel combustion engine in which the exhaust gases are introduced into a first and second coupled Helmholtz resonators, having respective first and second resonance containers, such that the ignition temperature of the soot is exceeded by periodic adiabatic compression of the oscillating exhaust column, actuated by igniting a first burner of a first one of the Helmholtz resonators which is timed in intervals corresponding to the resonance frequency, and a filter, arranged down-stream of a first one of the resonance housings, is regenerated by burning of the soot.
It is known from DE-OS 38 18 158 to introduce exhaust gases from Diesel combustion engines into two coupled Helmholtz resonators. The exhaust gases are fed into the resonators via the face of a first resonator. The first resonator is coupled with the second resonator via a resonance pipe. After passing the two resonators and the resonance pipe the exhaust gases reach a soot filter in which the Diesel soot is separated. In order to regenerate the soot filter, the second resonator, which is arranged directly before the soot filter, is equipped with a burner which may be operated in timed intervals. When the counter pressure in the resonator increases due to soot deposits, the burner is actuated periodically. The burner is ignited by a high voltage spark plug so that the exhaust gases inside the Helmholtz resonator are excited to carry out resonance oscillations. When after a pressure reduction a pressure build-up occurs again in the second resonator, an adiabatic compression of the exhaust gases occurs resulting in a temperature increase which is sufficient to ignite the soot at the neighboring filter thereby burning and destroying the soot deposit. A disadvantage of such a device is that the combustion engine is adversely affected by the first resonator because the pressure increase in the first resonator also increase the counter pressure in the exhaust line resulting in a power loss and an efficiency decrease of the combustion engine. By installing self-closing flap valves into the exhaust line, the negative feedback of the first resonator may be reduced, but due to the back pressure of the exhaust gases at the periodically closed flap valve the counter pressure is also increased causing the same negative feedbacks.
According to DE-OS 29 30 969 it is suggested to install a flap valve into the exhaust pipe after the filter which may be closed periodically for a short time so that the exhaust gases are stowed and compressed. Thus, the soot separated in the filter may be ignited and burned due to the temperature increase resulting from the compression. The disadvantage of such a device is that the flap valve also increases the counter pressure, thereby decreasing the effective power and the efficiency of the combustion engine.
It is therefore an object of the present invention to improve the method of the aforementioned prior art such that an effect of the regenerating system on the combustion engine is prevented without adversely affecting the quality of the regenerating process.